Method of and device for the manufacture of a cathode-ray tube for displaying coloured pictures, as well as cathode-ray tube manufactured by said method

ABSTRACT

A method of manufacturing a cathode-ray tube for displaying color pictures, comprising exposing a photosensitive layer on a support for the display screen to a narrow light beam the origin of which is situated in a plane corresponding to the deflection plane of the tube and moving the orign of the beam in the plane in accordance with the movement and deflection of the scanning electron beam in the working tube.

United States Patent Geenen et a1.

METHOD OF AND DEVICE FOR THE MANUFACTURE OF A CATHODE-RAY TUBE FORDISPLAYING COLOURED PICTURES, AS WELL AS CATI-IODE-RAY TUBE MANUFACTUREDBY SAID METHOD Inventors: Constant Joseph Maria Geenen;

Johannes Cornelis Adrianus Van Nes, both of Emmasingel.

Eindl'ioven Netherlands U.S. Philips Corporation, New York. NY.

Filed: Aug. 9, 1973 Appl. No.: 387,141

Assignee:

Foreign Application Priority Data Sept. 6. 1972 Netherlands o. 7212105US. Cl 96/36.I; 96/27 E; 354/1;

313/92 B Int. Cl G03c 5/00 Field of Search 96/361, 27 E; 313/92 PD.313/92 B. 114; 95/1; 354/1 Apr. 8, 1975 [561 References Cited UNITEDSTATES PATENTS 3.21 1.067 10/1965 Kaplan t. 95/1 3.667.947 6/1972 McKee96/361 3.689.267 5/1972 Little et a1. 96/36.] 1725.106 4/1973 Hosokoshi96/36.] 3.783.754 1/1974 Takemoto et al 96/361 Primary Exuminer-NormanG. Torchin Assistant E.\'amt'rterEdward C. Kimlin Attorney. Agent, orFirm-Frank R. Trifari; George B. Berka [57] ABSTRACT A method ofmanufacturing a cathode-ray tube for displaying color pictures,comprising exposing a photosensitive layer on a support for the displayscreen to a narrow light beam the origin of which is situated in a planecorresponding to the deflection plane of the tube and moving the orignof the beam in the plane in accordance with the movement and deflectionof the scanning electron beam in the working tube.

4 Claims. 3 Drawing Figures PATENTEDAPR 81975 SHEET 2 UF 2 METHOD OF ANDDEVICE FOR THE MANUFACTURE OF A CATl-IODE-RAY TUBE FOR DISPLAYINGCOLOURED PICTURES, AS WELL AS CATHODE-RAY TUBE MANUFACTURED BY SAIDMETHOD The invention relates to a method of manufacturing a cathode-raytube for displaying coloured pictures. in which a photosensitive layeris provided on a support for the display screen of the tube. a maskcomprising a pattern of light-transmitting regions is placed at a shortdistance before the photosensitive layer, the mask is scanned by anarrow light beam to form a pattern of exposed and unexposed regions onthe photosensitive layer, and the photosensitive layer is thendeveloped. The invention also relates to a device for carrying out sucha method and to a cathode-ray tube manufactured by such a method.

A method of the type mentioned in the preamble is known from BritishPat. No. 1.257.933. Moreover it is known that the direction of the lightrays which impinge upon the photosensitive layer via apertures in themask must correspond accurately with the direction of the electron rayswhich in the operating tube impinge upon the display screen via the sameapertures in the mask. Only then does the place of the luminescentregions ofthe display screen which are obtained after development of thephotosensitive layer correspond accurately with the place of theelectron spots. Differences generally cause serious colour defects. Itis therefore usual to use a correction lens which brings the virtualplace of the light source as readily as possible in agreement with thedeflection point of the relevant electron beam in the deflection coil ofthe cathode-ray tube.

However. with such a correction lens it proves in principle not possibleto obtain full agreement of the luminescent regions with the electronspots throughout the display screen. It is the object of the inventionto mitigate this drawback.

According to the invention, a method of the type mentioned in thepreamble is characterized in that the scanning light beam starts from apoint which during the scanning is moved in a predetermined manner whichcorresponds substantially to the scanning pattern ofthe electron beam inthe working tube. The scanning light beam may describe a large number ofparallel lines or a spiral-like track on the mask. A spiral-like trackmay have the advantage that the displacement of the starting point ofthe scanning light beam occurs more gradually in the case in which onlycomparatively small corrections are necessary along a circle having thecenter of the display screen as center.

A device for carrying out a method according to the invention preferablycomprises reflection means for reflecting a primary light beam. rotationmeans for rotating the reflection means about an axis of rotation. andtranslation means for translating rotation means in at least twomutually perpendicular directions, which reflection means arefurthermore tiltable relative to the rotation means about an axis whichextends at right angles to a plane through the said axis of rotation andthe axis of the said primary light beam. The operation of such a devicewill be described hereinafter with reference to an embodiment.

The invention will be described in greater detail with reference to theaccompanying drawing, of which FIG. 1 shows an exposure device forcarrying out a method according to the invention,

FIG. 2 shows a part of the device shown in FIG. 1 on an enlarged scale.and

FIG. 3 is a diagrammatic representation to explain the invention.

FIG. 1 shows an exposure device which comprises a housing I on which awindow part 2 of a cathode-ray tube to be manufactured is provided. Theinside of the window part 2 comprises a photosensitive layer 2. A shadowmask 4 having apertures 5 is mounted in the window part 2 in exactly thesame position as that in which the said shadow mask will afterwards bepresent in the operating cathode-ray tube. The photosensitive layer 3 isexposed via the apertures 5 in the shadow mask 4. In the present casethe apertures 5 are circular, which, however, does not mean arestriction for the more general application of the invention, so that apattern of exposed circular regions is formed on the photosensitivelayer 3. After the exposure, the photosensitive layer 3 is developed asa result of which in the present case a pattern of luminescent regions(phosphor dots) is formed on the window part 2. The exposure is totallycarried out three times. namely once from the deflec tion point of eachelectron beam. After the last development, the window part comprisesthree patterns of phosphor dots, namely in the present case a hexagonalpattern of green. red and blue luminescent phosphor dots. Thephotosensitive layer 3 may consist ofan inorganic photosensitive layer.which becomes insoluble by exposure to light. The phosphor may alreadybe present in said layer. in which case development is carried out bydissolving the unexposed parts ofthe layer and rats ing them away. Thephotosensitive layer 3 may also consist of a photoconductive layer on aconductive substratum. In that case the photoconductive layer isprovided with an electric surface charge which leaks away from theexposed parts of the layer. Phosphor particles charged with the samesign are then deposited on the photoconductive layer 3, which particlesadhere only to the exposed parts of the layer since they are repelled bythe charge on the unexposed parts. Similar methods and all kinds ofvariations are generally known and need not be further explained. Theymay also be used for applying a non-reflecting layer between thephosphor dots so as to reduce the reflection of ambient light.

The exposure which forms the subject matter of the present invention iscarried out by means of a light beam 6 which is formed by reflection ofa primary light beam 7 in the center of a mirror 8. The plane of themirror 8 is at right angles to the plane of the drawing of FIG. 1. Themirror 8 can be tilted about an axis 10 at right angles to the plane ofthe drawing. When the mirror 8 is tilted about the axis 10, the lightbeam 6 describes a line on the photosensitive layer 3. The mirror 8 withthe axis 10 are rotatable about the axis of rotation 9. When the mirror8 is rotated about the axis 9, the light beam 6 describes a circle onthe photosensitive layer 3. By the combination of a slow tilting aboutthe axis I0 and a rapid rotation about the axis 9, the light beam 6describes a spiral on the photosensitive layer 3. The pitch of saidspiral must be of the order of magnitude of the diameter of the lightbeam 6 so that each place of the photosensitive layer is exposed. Therotation and tilting of the mirror in such manner that the primary lightbeam 7 remains always directed on the center of the mirror 8 is carriedout by means of the device 11 which will be described with reference toFIG. 2.

FIG. 2 shows the device denoted in FIG. 1 by I] for the rotation andtilting of the mirror 8 and for the movement of the center of the mirror8. The light beam 6 is formed by reflection of a primary light beam 7 onthe mirror 8. The mirror 8 can be tilted about the axis 10 which in theposition shown is at right angles to the plane of the drawing. Thetilting of the mirror 8 is obtained by means of the device 12. Themirror 8 with the axis 10 and the device 12 are mounted on rotationmeans 13 which are rotatable about the axis 9. The primary light beam 7is obtained by reflection of a light beam 14 on a mirror [5. The mirror15 is rigidly mounted relative to the rotation means 13 so that thelight beam 7 always remains directed on the center of the mirror 8during the rotation ofmirror l5 and mirror 8 about the axis 9. since thelight beam 14 is parallel to the axis 9. The light beam I4 is formed byreflection of a light beam 16 on a mirror 17. The mirror 17 can be swungrelative to the mirror 15 about the axis 18 which is parallel to theaxis 9. As a result ofthis the mirror 17 during rotation of the axis 9can always remain directed on the light beam 16. The light beam 16 isformed by reflection of a light beam 19 from a mirror 20 which can beswung about an axis 21. The telescopic connection 22 ensures that themirrors [7 and 2t) always re main directed to each other. The light beam[9 finally is produced by the lamp 23 in the reflector l4 and collimatedby the lens 25. It is also possible to produce the light beam by meansof a laser device.

So the scanning light beam 6 starts from the center of the mirror 10.This center can be moved in two directions which preferably are mutuallyat right angles by means of the slide 26 and the slide 27. Thedeflection point of a deflected electron beam can be defined as thepoint ofintersection ofthe tangent at the axis of the deflected beam atthe area of the display screen with a plane which extends at rightangles to the axis of the tube and may be chosen arbitrarily. This planeis generally chosen through the center of the deflection coil system andis then termed deflection plane. During the deflection. the deflectionpoint moves in the defleo tion plane. The nature of the said movement isinter alia closely associated with the nature of the deflection coilused. The deflection angle of the electron beam is defined as the anglebetween the tangent at the axis of the deflected beam at the area ofthepicture screen and the axis of the tube.

In FIG. 3. the \'J plane is the deflection plane of a given cathode'raytube for displaying coloured pictures. The tube in question has a ratherflat display screen having a radius of curvature of 1.017 mm. Thedeflection plane is at a distance of 273 mm from the inner surface ofthe display screen. The deflection point of a non-deflected electronbeam coincides with the origin 0 of the deflection plane. The axis ofthe cathode-ray tube intersects the deflection plane in A. The distance0A corresponds to the eccentricity of the electron beam in questionrelative to the axis of the tube. since the relevant tube comprisesthree electron guns in delta arrangement. The projection on thedeflection plane of the target on the display screen of an electron beamhaving a deflection angle 1) is denoted by P. The direction in which theelectron beam is deflected is denoted by the angle ill relative to they-axis. The place in the deflection plane of the deflection point D ofsaid electron beam is defined by the coordinates R and T which are eachfunctions of d) and (it. For the relevant tube with associateddeflection coil it holds that:

R 13mb) 40 (rg /z o) rgd) 3.2 sin d) {l (cos 2111] /)}sin :11 Ttrti, lrj3.2 sin ti: {l+ (cos 2 cbl/Hcos '11.

in these equations R and T are expressed in mms.

The center of the mirror 8 should always coincide with the deflectionpoint D. The movement of the deflection point D in the deflection planeis ensured by the slides 26 and 27 as a function of the angle (b (FIG.2] and the angle ll! (FIG. 3). which angle d) is obtained by tilting themirror 8 relative to the rotation means 13. and which angle ll! isobtained by the rotation of the ro tation means 13 about the axis 9.

Instead of the slides 26 and 27 which move the center of the mirror 8 inthe deflection plane in two mutually perpendicular directions. it isalso possible to use slides which move the deflection point in a radialand aximuthal direction in the deflection plane. It is also possible todefine the deflection point differently and to cause the center of themirror 8 to make. for example. a movement parallel to the axis 9 and ina direction at right angles thereto.

What is claimed is:

LA method of manufacturing a cathode-ray tube for displaying colorpictures. comprising the steps of: providing a photosensitive layer on asupport for the display screen of the tube. placing a mask having apattern of light-transmitting regions at a short distance in front ofthe photosensitive layer. scanning mask by rotating a narrow light beamabout an axis which is parallel to the main axis of the tube. tiltingthe light beam about an angle with respect to the axis of rotation and,at the same time. subjecting the origin of the light beam to atranslational movement in two mutually perpendicular directions in aplane corresponding to the deflection plane of the working tube. thetranslational movement being a function of the angle of rotation and ofthe angle of tilting to provide a scanning pattern for the electron beamin the working tube. and developing the resulting pattern of exposed andunexposed regions on the photosensitive layer.

2. A method as claimed in claim 1, characterized in that the scanninglight beam is formed by reflection of a primary light beam by means ofreflection means and that said reflection means are moved during thescanning to provide the previously determined compound movement.

3. A method as claimed in claim 1 wherein the scanning light beamdescribes a large number of parallel lines on the mask.

4. A method as claimed in claim 1 wherein the scanning light beamdescribes a spiral-like track on the mask.

1. A METHOD OF MANUFACTURING A CATHODE-RAY TUBE FOR DISPLAYING COLOR PICTURES, COMPRISING STEPS OF: PROVIDING A PHOTOSENSITIVE LAYER ON A SUPPORT FOR THE DISPLAY SCREEN OF THE TUBE, PLACING A MASK HAVING A PATTERN OF LIGHT-TRANSMITTING REGIONS AT A SHORT DISTANCE IN FRONT OF THE PHOSTOSENSITIVE LAYER SCANNING MASK BY ROTATING A NARROW LIGHT BEAM ABOUT AN AXIS WHICH IS PARALLEL TO THE MAIN AXIS OF THE TUBE, TILTING THE LIGHT BEAM ABOUT AN ANGLE WITH RESPECT TO THE AXIS OF THE TUBE, TILTING AT THE SAME TIME, SUBJECTING THE ORIGIN OF THE LIGHT BEAM TO A TRANSLATIONAL MOVEMENT IN TWO MULTICLLY PERPENDICULAR DIRECTIONS IN A PLANE CORRESPONDING TO THE DEFLECTION PLANE OF THE WORKING TUBE, THE TRANSLATIONAL MOVEMENT BEING A FUNCTION OF THE ANGLE OF ROTATION AND OF THE ANGLE OF TILTING TO PROVIDE A SCANNING PATTERN FOR THE ELECTRON BEAM IN THE WORKING TUBE, AND DEVELOPING THE RESULTING PATTERN OF EXPOSED AND UNEXPOSED REGIONS ON THE PHOTOSENSITIVE LAYER.
 2. A method as claimed in claim 1, characterized in that the scanning light beam is formed by reflection of a primary light beam by means of reflection means and that said reflection means are moved during the scanning to provide the previously determined compound movement.
 3. A method as claimed in claim 1 wherein the scanning light beam describes a large number of parallel lines on the mask.
 4. A method as claimed in claim 1 wherein the scanning light beam describes a spiral-like track on the mask. 